Paper machine forming wire



y 1961 L. HORNBOSTEL ET AL 2,992,681

PAPER MACHINE FORMING WIRE Filed Sept. 22, 1955 Lia,

PRIOR 4/27- Eq 2 mloknz-r -3 iVZ EUZEFE LLOYD HORNBOSTEL EDGAR. J.JusTus fawn/2 D. BEACHLER 2,992,681 PAPER MACHINE FORMING WIRE LloydHornbostel, Edgar J. Justus, and Edward D. Beachler, Beloit, Wis.,assignors to Beloit Iron Works, Beloit, Wis., a corporation of WisconsinFiled Sept. 22, 1955, Ser. No. 535,979 2 Claims. (Cl. 162-348) Theinstant invention relates to Fourdrinier type paper making machines, andmore particularly, to an improved Fourdrinier type paper machine formingwire and to an improved method and apparatus for driving a loopedtraveling band or forming wire, such as the forming wire of aFourdrinier type paper making machine.

Although the instant invention may have application in a number offields, it is uniquely adapted to the operation of paper machines, andparticularly to the operation of the forming wires in paper machines,and the invention will be described in detail with respect to thisparticular aspect. In the operation of the forming wire heretofore inpaper machines, the forming wire was mounted with an upper run extendingfrom a breast roll at the rear end to a suction couch roll at theforward end of the top reach of the Wire, with suction boxes beneath thetop reach and adjacent the couch roll, and the bottom reach or returnreach of the looped wire is supported on a number of return rolls.Heretofore, it had been the accepted pactice to drive the forming Wirethrough the suction couch roll (or suction couch rolls, if a pair ofsuction couch rolls are used at the forward end of the loop). Helperdrives might connect the main drive (associated with the suction couchroll) to drives for other rolls, so that these rolls might be driven atthe speed of the travelling wire to avoid frictional drag duringengagement therewith, but were not used to drive the wire. In the caseof the breast roll, drive mechanisms therefor had not been successful,because of the tendency for driving of the breast roll to causeirregularities in the smooth operation of the wire just beyond thebreast roll whereat initial web formation takes place. The minimumtension on the wire occurs generally in the region of the breast roll.As the wire passes over the suction boxes, a substantial frictional dragis applied to the Wire and the tension on the wire is at a maximumbetween the suction boxes and the (first) suction couch roll. Dependingupon the general type of the paper machine, this maximum tension inpresent day paper machines may range from as little as about 20 poundsper inch to as much as about 100 pounds per inch, but is usually about30-60 pounds per inch (of width).

As a typical example of a modern-day paper machine operation, the wiremay be about 200 inches wide and have a travelling speed of 2000 feetper minute with a total Fourdrinier load of 250 horsepower. The suctioncouch roll in such a paper machine is the drive roll. Since anappreciable amount of tension must be maintained on the wire at allparts of the travel thereof, the tension on the wire at the oifrunningside of the suction couch roll is usually about 12 pounds per inch. Themaximum tension between the suction boxes and the suction couch roll (orat the forward side of the suction boxes) is 12 pounds per inch plus theamount of tension imparted to the wire by the 250 horsepower work inputat the couch roll, which may be calculated as follows: i

250 H.P. 33,000 ft.-lb./min.

2000 ft./min. 200 in. 2206 Total max. tension=12+20.6= 32.6 lb./in.

The foregoing indicates the operating conditions for a typical papermachine; and operating conditions such as these have been used for anumber of years in paper machines. The operation herein described oftenresult States Patent dewater the stock therethrough; and to 2,992,681Patented July 18, 1961 in a wire change about once every three to fivedays, which is necessitated by ordinary wear on the wire. The wirechanges involves a production shut down of an appreciable period of timeplus the cost of a new wire (which itself may be as much as $4,000.00),although the production loss is the greatest financial loss hereinvolved. For years, this has been recognized as one of the necessarycosts of the operation of a paper machine because it was universallyassumed that the wire Wear was caused primarily by the suction boxes. Itwill also be appreciated that, in view of the extremely expensive natureof paper machines and also the highly developed skill of engineersinstalling such paper machines, the paper machine operators do not makerandom changes in the operation of the paper machines, nor do they lookwith any favor toward suggestions by their own or the installingengineers concerning radical departures in the paper machinearrangement. There is too much at stake to risk such substantial losses,when the operation of the usual paper machine was at least sufiicient toproduce what amounts to an economically adequate result.

For one thing, the general design of the forming wire itself has notchanged appreciably over a number of years. The wire is actually a wovenproduct obtained by weaving warp wires in generally parallel peripheralalignment with respect to the ultimate wire loop (or aligned in thedirection of travel for the wire) with chute or cross-wires. Heretofore,the cross-wires were substantially straight or uncrimped extendinggenerally perpendicular to the warp wires in the direction of travel,and the warp wires were woven in a generally serpentine configurationover one cross-wire, under the next, over the next, etc. This had beenstandard wire design for a number of years using the conventional bronzewires employed in the formation of the paper machine forming wire.

The instant invention, however, is based upon the discovery that certainspecific alterations can be made in the wire design so as to increasethe wire life several hundred percent, or to as much as two or threeweeks. In combination with the alterations in the wire design orstructure, it has also been found that altered drive means or drivingarrangements can be used to obtain still greater wire life. For onething, it has been found that altering the forming Wire structure so asto employ substantially straight warp wires and pre-crimped or curvingcrosswires to Weave the serpentine path results in a unique improvementin wire life. Also, the use of this improved wire structure in anarrangement wherein driving of the forming wire is not carried out withthe suction roll or suction couch roll, but rather is carried out usinga plain surfaced roll or rolls results in a still greater improvement inwire life.

It is, therefore, an important object of the instant invention toprovide an improved forming wire, and an improved method and apparatusfor driving of the forming wire in a paper machine or the like.

Another object of the instant invention is to provide an improvedFourdrinier type paper making machine comprising a looped forming wirehaving an elastic modulus in tension of at least 15,000 pounds per inchof width, and a plurality of supporting rolls driving the wireperipherally of the loop. i

Still another object of the instant invention is to provide an improvenmethod of forming paper in a Fourdrinier type paper machine thatcomprises providing a looped forming wire with an elastic modulus intension of at least 15,000 pounds per inch, flowing stock onto the wire,and frictionally engaging the wire to drive it over stationary suctionboxes and a rotary suction couch roll to provide an improved Wire foruse in said method.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed disclosure thereof and the drawings attached heretoand made a part hereof.

On the drawings:

FIGURE 1 is a diagrammatic View of a Fourdrinier machine wirearrangement;

FIGURE 2 is a detail top plan view of a portion of a forming wire of thetype used in the prior art;

FIGURE 3 is a detail sectional view taken substantially along the lineIIIIII of FIGURE 2;

FIGURE 4 is a detail top plan view of a portion of a wire embodying theinstant invention;

FIGURE 5 is a sectional detail view taken substantially along the lineV-V of FIGURE 4;

FIGURE 6 is a sectional detail view taken substantially along the lineVI-VI of FIGURE 4; and

FIGURE 7 is a detail sectional view similar to that of FIGURE 6, exceptshowing a different embodiment of the instant invention.

As shown on the drawings:

In FIGURE 1, the wire arrangement for a Fourdrinier type machineindicated generally by the reference numeral 10 comprises a loopedforming wire 11 and a plurality of rolls supporting the wire 11including a perforate surfaced suction roll 12 (with suction area 12a)within the loop of the wire 11, a breast roll 13, a turning roll 14, andplain surfaced return rolls 15, 16 and 17, plus an adjustable tensioningroll 18.

The upper run 11a of the wire 11 passes over the breast roll 13, atwhich an inlet box 17 flows stock onto the upper run 11a of the wire 11.The direction of travel of the wire is indicated by arrows; and it willbe seen that the wire passes over the breast roll 13 and travelsforwardly therefrom over suction boxes 18 which are stationary and whichdewater the web carried on the wire 11 as it passes over the suctionboxes. The wire 11 then travels'forward from the suction boxes 18 andover the couch roll 12 and then around the turning roll 14 and finallyover the return rolls 15, 16 and 17 and the tensioning roll 18. Theremay, of course, be a number of additional return rolls positioned Withinor without the loop of the wire 11 in the prior art arrangement.

In the prior art machines, suitable drive means in the form of a motor19 was connected to the couch roll 12 by any suitable connection andsubstantially the entire driving of the wire 11 was accomplished at thecouch roll 12 so that substantially the entire tension change took placethereover. For example, in the prior art, the tension T just after thesuction boxes 18 would be 32.6 pounds per inch, and the tension T justafter the suction roll 12 would be 12 pounds per inch. The tensionchange over the turning roll 14 and the return rolls 15, 16 and 17 wouldbe negligible so that the tension T just before the suction boxes 18would also be about 12 pounds per inch. In actual practice, the maximumtension T between the suction boxes 18 and the suction roll 12 ranged inthe prior art from at little'as about 20 pounds per inch to as much asabout 100 pounds per inch, although the maximum tension T is usually 30to 60 pounds per inch in most paper machines. The suction boxes 18 arestationary and they apply a rather substantial drag to the wire 11passing over, so that the tension T before the suction boxes 18 willoften be found to be within the range of about 10% to about 50% of themaximum tension T but in no case in the prior art has T exceeded 15pounds per inch. Expressed in other terms, the tension increase (T -Tacross the suction boxes is usually about 10 to 60 pounds per inch; andin the prior art the couch roll furnished 80 to 100% of the wire drive,thus creating a tension drop T T substantially equal to T -T Using anarrangement such as that here described in connection with the priorart, the wire 11 must be changed about every three to five days. In someinstances helper drives are employed for the turning roll 14 and returnrolls 15,

16 and 17 so that such rolls will be driven at the speed of the wire 11to avoid frictional drag on the wire 11, but such helper drives did notimpart in the prior art any actual drive to the wire 11 so as to effecta tension reduction thereover. As previously mentioned, a separate drivefor the breast roll 13 is not ordinarily practical because it isimportant that the wire top run 11a be uniformly tensioned when itreceives the stock from the head box 17.

Referring now to the actual distinctions shown in FIG- URE 1 over theprior art, it will be seen that drive mechanisms are provided for eachof the rolls 14, 15 and 16, as indicated diagrammatically at 14a, 15a,16a and 17a, respectively. A main drive mechanism 1511 (as hereindicated with double lines interconnecting the drive mechanism 15a andthe roll 15) is provided for the return roll 15. In the usual papermachine arrangement, the main drive 15a is a speed regulated drive whichhas direct mechanical connection to the motor; and as previouslymentioned, the main drive heretofore was the drive for the couch roll12. This change is particularly important, as will be brought outhereinafter, and in the instant device the main drive, which serves tocontrol the actual wire speed, is the drive 15a for the return roll 15.

Torque regulated helper drive mechanisms 19, 14a, 16a and 17a are alsoused preferably in the practice of the instant invention to impartrotary movement to the rolls 12, 14, 16 and 17, respectively, but onlythe rolls 14, 16 and 17, which are imperforate surfaced rolls, aredriven so as to actually assist in driving the wire 11. In helper drivemechanisms, the usual arrangement calls for a variable voltage D.-C.electric motor which drives the roll 14, 16 or 17 at predeterminedtorque to impart pre determined drive to the roll. As will beappreciated, a helper drive such as the helper drive 19 might be usedmerely to rotate the roll 12 for example at the speed of the wire so asto avoid dragging the wire over the roll; and this is also possible inconnection with the operation of the rolls 14, 16 and 17, although notpreferable. In actual practice, the paper machine of FIGURE 1 ispreferably driven so that the maximum tension T is about 55 pounds perinch, the tension T at the oifrunning side of the couch roll 12 is about50 pounds per inch, the tension T at the offrunning side of the turningroll 14 is about 4 5 pounds per inch, the tension T at the 0&- runningside of the main drive roll 15 is about 30 pounds per inch, the tensionT at the oifrunm'ng side of the return roll 16 is 25 pounds per inch andthe tension T at the oflrunning side of the last return roll 17 is 20pounds per inch which is also substantially the tension T at theoncoming side of the suction boxes 18. This results in an improvement inwire life, using the prior art wire structure, such that the wire lifeis increased to as much as two weeks; but it has been found that acomparable improvement in wire life can be obtained using the prior artdrive arrangement and an improved wire structure to be described herein,or a still greater incease in wire life to as much as three weeks can beobtained using the improved wire structure herein described as well asthe improved drive arrangement just described in connection with FIGURE1.

Although it is not desired to limit the invention to any particulartheory, it is now believed that there is an explanation for theunexpectedly superior results here obtained. First of all, elaboratetests have been made recently to ascertain the character of the formingwire and its various properties which might lead to answers to thevarious problems presented in this art; and it has been found thatforming wires used in the prior art have all had an elastic modulus intension of 6,000 pounds per inch to 10,000 pounds per inch, at the verybest. A higher elastic modulus was not recognized as being desirable inthe prior art. In fact, there was no appreciation in the prior artconcerning differences in the moduli of elasticity or any possibleeffect that this particular property might have on wearing of the wire.As previously calculated, however, the tension change in a typical priorart paper machine (primarily across the couch roll) may involve as muchas 20.6 pounds per inch. Since the prior art forming wire was elastic toa certain extent it follows that changes in length would have to takeplace at the point where changes in tension take place. Such changes arecontinuous in character and the magnitude thereof depends upon the speedof the traveling wire. For example, in a wire traveling at a speed of2000 feet per minute and having a modulus of 8,600 pounds per inch, thechange in length of the wire continuously taking place at the main drivecouch roll of the prior art may be cauculated as follows, where AL isthe change in length:

20.6 lbs/in. AL 2000 ft./min.

20.6 lbs/in. X2000 ft./min.

8600 lbs/in. AL=4=.8 ft./min.

This means that there was constant sliding or slipping, better describedas creepage, taking place between the wire and the driving couch roll inthe prior art. This constant slippage or creepage resulted in excessivewear on the wire. This explains why greatly reduced wire wear can beobtained by driving the wire with an imperforate surfaced roll, such asthe roll 15, which will not have the abrading effect on the wire thatthe perforate surfaced couch roll has. In this respect, the prior artconcept of employing the couch roll as the main drive roll for imparting80 to 100% of the drive to the wire is contradicted completely and,instead, it has been found that it is important to use plain surfacedrolls, such as the rolls 14, 15, 16 and 17 to impart 75 to 100% of thedrive to the wire and, in fact, it has been found particularlyadvantageous to employ imperforate surfaced rolls 15 and 17, positionedoutside of the loop of the wire 11, to impart at least 50% of the driveto the wire, and preferably as much as 75% or more. As will beappreciated, the advantages here obtained may be obtained using atension drop of or even less across the couch roll and across any otherrolls positioned within the loop of the wire 11, if further advantage isto be taken of the use of driving rolls positioned outside the loop ofthe wire.

Still another important aspect of the instant invention, however,resides in the use of a forming wire of altered or improved structure,and this aspect of the invention can best be described in connectionwith FIG- URES 2-7, inclusive. Referring first to FIGURES 2 and 3, itwill be seen that the piror art wire W comprised a plurality ofgenerally parallel warp wires 20, 21, 22, 23, etc. which were alignedperipherally with respect to the loop of the wire and extended in thedirection of wire travel (as indicated by the arrow in FIGURES 2 and 3).Cross-wires 30, 31, 32, 33, etc. were also provided and the cross-wireswere substantially uncrimped, or extended in straight lines. The warpwires, as indicated in FIGURE 3, passed over and under the cross-wiresand wove a generally serpentine path, whereas the cross-wires remainedsubstantially straight. This structure came about as a result of theparticular weaving methods which have been used for some time in theprior art without any thought that a diiferent structure could be usedor might be desirable.

In contrast, the instant invention provides as one of its features thechanging of the general structure of the forming wire W of the prior artso as to obtain a structure of a wire W shown in FIGURES 4, 5 and 6. Aswill be seen in FIGURE 4, wherein corresponding elements are givenprimed reference numerals, there does not appear to be much differencein the top plan view 8600 lbs/in.

of the wires W and W, but FIGURE 5 which is a view corresponding toFIGURE 3 shows clearly that the warp wire 21' is a straight wire,whereas the cross-wires 30', 31', 32', 33, etc. clearly weave aserpentine path over and under successive warp wires. This is alsobrought out in FIGURE 6, which shows a view at right angles to the viewof FIGURE 5 and it will be noted that the overall appearance of the viewof FIGURE 6 is comparable to the overall appearance of the view of FIG-URE 3, but these views are taken at right angles to each other usingdifferent wire structures. In making the wire structure W, it may bedesirable to pre-crimp the crosswires 30, 31, etc. or it may bedesirable to change the weaving apparatus to assure that the warp wiresor longitudinally extending wires 20, 21', etc. will remainsubstantially straight. The change in structure embodied in the wirestructure W results in an increase in the elastic modulus (using thesame bronze wires) at least up to 15,000 pounds per inch. This increasein elastic modulus greatly reduces the tendency for the wire to wear(far out of proportion to the mere increase in the modulus from thatused in the prior art), thereby indicating that the wearing of the wireinvolves certain unknown factors.

It has been found, however, that increasing the elastic modulus intension to at least 15,000 pounds per inch is of particular importancein obtaining advantages in reduction in wire Wear. Changing of the wirestructure to the structure W here indicated is preferable, althoughcertain other advantages may be obtained, for example, by using strongermetals such as Monel metal in weaving the forming wire and changing thesizes of the wires employed in weaving the forming wire. Particularly,it is advantageous to employ warp wires that are at least about twice asbig as the cross-wires in cross-sectional area, and preferably even moreup to about five times as big. The wire sizes may not be totallydisproportionate. The increase in the modulus is, of course, unlimitedas far as advantages of the invention are obtained, since a modulus ofinfinity would presumably result in no wear at all at a driving roll.

The arrows in FIGURES 4 and 5 indicating the direction of travel of thewire in these views bring out more clearly the differences in structurebetween the wire of FIGURE 2 and the wire of FIGURE 4.

In FIGURE 7, a view is shown comparable to the view of FIGURE 6 (i.e. atright angles to the direction of travel of the wire) for a differentwire structure embodying the instant invention. In FIGURE 7, the warpwires 41, 42, etc. actually comprise a bundle of smaller wires formedtogether in a cable, the smaller wires being indicated as 41a, 41b, etcand 42a, 42b, etc. The cross wires 51, 52, etc. are, of course, crimped.or weave a serpentine path over and under successive warp wires in themanner hereinbefore described, whereas the warp cables 41 and 42 remainsubstantially straight. In the embodiment of FIGURE 7 a plurality ofwires 41a, 41b, etc. are combined in the cable 41 so as to obtain acrosssectional area in the cable 41 that is about three or four times asbig as the cross-sectional area of the cross wire 51, but a combinationof wires 41a, 4112, etc. is used in order to impart the desiredflexibility to the warp cable 41 while effecting the desired increase inthe elastic modulus in tension.

In its broadest aspects, the invention herein resides in an improvedmethod of forming paper in a Fourdrinier type paper machine, thatcomprises providing a looped forming wire W with an elastic modulus intension of at least 15,000 pounds per inch, flowing stock onto the wireand, frictionally engaging the wire to drive it over stationary suctionboxes and a rotary suction couch roll to dewater the stock therethrough.Also, an aspect of the invention comprises carrying out the foregoingprocess while maintaining the warp wires in the forming wire W insubstantially straight alignment in the direction of travel over thesuction box. The wire must, of course,

be supported with at least one perforate surface in the form of thesuction boxes and another perforate surface in the form of the couchroll and the wire must be driven over these surfaces. As the wire W isurged over such perforate surfaces as the suction boxes 18 and the couchroll 12, the wire is also urged against both of these perforate surfacesby creating a pressure differential across the wire.

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts of thepresent invention.

We claim as our invention:

1. In a Fourdrinier type paper making machine, a looped forming Wirehaving substantially straight warp wires in generally parallelperipheral alignment extending in machine direction and cross wiresextending transverse to machine direction and woven over and undersuccessive warp Wires, and a plurality of rolls supporting the wire loopand driving the wire peripherally of the loop.

2. In a Fourdrinier type paper making machine, a looped forming wirehaving substantially straight warp wires in generally parallelperipheral alignment extending in machine direction and cross wiresextending transverse to machine direction and Woven over and undersuccessive warp wires and about one-half to one-fifth thecross-sectional area of the warp wires, and a plurality of rollssupporting the wire loop and driving the wire peripherally of the loop.

References Cited in the file of this patent UNITED STATES PATENTS1,525,881 'OBrien Feb. 10, 1925 1,593,668 ONeill July 27, 1926 1,767,814Reynolds June 24, 1930 2,003,123 Specht May 28, 1935 2,039,780 Darby May5, 1936 2,227,669 Parrett Jan. 7, 1941 2,392,150 Hornbostel et a1 Ian.1, 1946 2,755,047 Henke July 17, 1956 FOREIGN PATENTS 389,068 GreatBritain Published 1933 837,607 France Nov. 12, 1938 OTHER REFERENCESManufacture of Pulp and Paper, third edition, vol. 5, section 1, pages81 and 82 (1939), Published by McGraw- Hill Book Co., New York, N.Y.

